The present invention relates to intraocular lenses, implanted into the eye for the correction of vision.
A posterior chamber phakic refractive lens (PRL) is surgically implanted behind the iris and in front of the human natural crystalline lens for correcting ametropia, such as myopia, hyperopia, and astigmatism. PRLs should fit inside the eye properly in order to achieve the intended design functions. Because eye sizes are different from one patient to another, various sizes of PRLs must be used for different patients. Even for the same patient, PRLs based on different design principles require different sizes in order to achieve the intended benefit. For example, a PRL of a free-floating design would require that the length of the PRL be approximately same or slightly less than the sulcus-to-sulcus distance (see FIG. 1). In this way, the PRL can be loosely held in place behind the iris and in front of the human natural crystalline lens, hence the free-floating design feature is achieved. On the other hand, a PRL of sulcus-fixed design would require that the length of the PRL is larger than the sulcus-to-sulcus distance (see FIGS. 2, 3). This way, the PRL can be anchored in the sulcus and at the same time it can vault towards the anterior chamber due to the oversized length. The longer the PRL, the stronger the anchoring force and the more the PRL vaults towards the anterior chamber. In the Figures of this application, 1 represents the cornea, 2xe2x80x94the iris, 3xe2x80x94the natural lens, 4xe2x80x94the aqueous humor, 5xe2x80x94the ciliary sulcus, and 6xe2x80x94the phakic refractive lens (PRL).
However, the excessive anchoring force and vaulting due to the oversized length of the PRL may cause a number of undesirable effects on the eye. First, when the PRL is too long, it will cause stress on the ciliary body, zonule, and the natural crystalline lens. Stress on the ciliary body may result in the pupil ovalization. Stress on the zonule may interfere with accommodation in the eye, and stress on the natural crystalline lens may cause capsular opacification or cataract formation. Second, the excessive vaulting may increase the friction force between the iris and the anterior surface of the PRL when the iris dilates or contracts corresponding to light conditions. This increased friction may result in iris chaffing or iris pigment dispersion. Third, the excessive vaulting may decrease the anterior chamber depth. Consequently, it increases the risk of endothelial cell loss. Fourth, excessive vaulting decreases the angle of the anterior chamber. As a result, it slows down the aqueous humor outflow and, therefore, may increase the risk of elevating intraocular pressure, i.e. glaucoma. Lastly, since the ciliary body and zonules are living tissues, they may gradually yield to the stress at the point of PRL contact. The initial gap between the PRL and the natural crystalline lens created by the vaulting of the PRL due to its oversized length may gradually decrease as eye tissues yield to the stress. It may lead to direct contact of the PRL with the natural crystalline lens. This may lead to the capsular opacification of the natural crystalline lens.
For the reasons discussed above, it would be desirable to have an anatomically compatible PRL design, which can be fixated in the sulcus, without the problems caused by the oversized length. The present invention provides PRLs with an xe2x80x9cadjustable hapticxe2x80x9d design which will prevent the PRL from vaulting excessively. Therefore, it avoids problems otherwise caused by the oversized length of the PRL. Furthermore, the adjustable haptic design allows for a one-size-fits-all design PRL.
There are a number of patents describing the PRL concept or specific related lens designs. U.S. Pat. No. 4,585,456, Blackmore, issued Apr. 29, 1986, discloses a phakic intraocular lens (IOL) composed of flexible materials positioned against the natural lens of the eye and being held in place immediately adjacent to the natural lens and the ciliary sulcus. It also discloses that surgeons need to select the proper optics for the particular eye. However, there is no disclosure of the phakic IOL""s size or the method for selecting the proper size.
Fedorov has several U.S. patents describing new features of phakic refractive lenses for avoiding potential complications. In U.S. Pat. No. 5,480,428, issued Jan. 2, 1996, Fedorov discloses a phakic lens design that has an opening at the center of the optic body. This open hole allows aqueous humor flow through the lens body, thereby preventing IOP (intraocular pressure) elevation. Fedorov, in U.S. Pat. No. 5,258,025, issued Nov. 2, 1993, discloses that post-operative inflammation, caused by the contacting of lens-supporting elements with the ocular tissue, can be prevented by moving the supporting elements to the periphery of the phakic lens. The diameter of the position elements is from about 10 mm to about 10.5 mm. The distance of diametrically opposite ends of the supporting elements is taught to not be less than the diametrical distance between the Zinn""s zonules or Zinn""s ligaments and is in the range of 11.5 to 12.0 mm (FIG. 4). In the diagram of the IOL, 11 represents the haptics (supporting elements) of the lens. The Zinn""s zonules are strong enough to hold the supporting elements in place without causing inflammation. Fedorov, in U.S. Pat. No. 5,766,245, issued Jun. 16, 1998, discloses an IOL for correcting moderate t o severe hypermetropia. The length of the IOL is from 10 to 13 mm. However, there is no disclosure of a method for selection of a properly sized PRL for an individual patient. Furthermore, in none of the Fedorov patents was a PRL design disclosed where the haptic length of the PRL can be adjusted for eyes of various sizes.
Kelman, in U.S. Pat. No. 4,769,035, issued Sep. 6, 1988, discloses a surgical procedure for correction of the eyesight of a human eye by implanting an artificial lens between the iris and anterior surface of the human lens. It is a multi-step procedure including the following two steps. First, the patient""s refractive error is measured so that the artificial lens can be properly selected with desirable optical power for the patient. Second, the shape of the anterior surface of the patient""s natural lens is determined so that the artificial lens can be selected to have its posterior surface shape conforming to the anterior surface of the patient""s natural lens. In other words, the posterior surface of the optic portion of the artificial lens is in substantial face-to-face contact with the anterior surface of the patient natural lens. Kelman also pointed out that ultra-sonography technology (A scan or B scan) can be used for determining the shape of the patient""s natural lens and that the longitudinal length of the artificial lens is approximately 13 mm. Nevertheless, Kelman""s lenses are not designed for adjusting their overall haptic length for fitting various eye sizes.
Lastly, Valunin""s U.S. Pat. No. 6,015,435, issued Jan. 18, 2000, discloses a PRL and a method of fitting the PRL between the iris and the anterior surface of the human natural lens. The PRL""s size and dimensions are selected in such a way that the haptic bodies of the PRL cannot contact the outermost circumference of the ciliary sulcus of the wearer at the same time. Among other disclosures, Valunin indicates that the maximum diagonal haptic body dimension is preferably from about 10.5 mm to about 11.5 mm (FIG. 5). However, Valunin is silent on whether the haptic design is size adjustable.
Accordingly, there is a need for an anatomically compatible PRL design where the haptics, when needed, can be adjusted for fitting eyes of various sizes. In other words, PRL designs of the present invention can be size adaptive according to the dimensions of the individual eye. These lenses avoid the problems otherwise caused by oversized haptic length in a relatively small eye.
The present invention relates to an anatomically compatible phakic refractive lens for the correction of ametropia, structurally adapted to be positioned in the posterior chamber of the eye, comprising:
(a) an optical body having a diameter of from about 3 to about 7 mm; and
(b) at least one haptic body which comprises:
(i) a first portion which is attached to and extends from said optical body, has a diagnostic distance of from about 8 to about 11 mm, and which is structurally adapted to conform in whole or in part to the anterior surface of the natural crystalline lens of the eye;
(ii) a second portion which extends outward from the outer edge of said first portion, and has a diagnostic distance of from about 11 to about 14 mm; and
(iii) a transition zone between said first portion and said second portion structurally adapted to permit said second portion to conform to the shape of the ciliary sulcus of the eye.
In preferred lenses, there are two haptics which extend in opposite directions from the optical body; the transition zone includes a score or groove in the lens surface or includes a change in the radius of curvature of the posterior surface of the haptic; the posterior surface of the first haptic body has the same radius of curvature as the posterior surface of the optical body; and the second haptic portion of the lens may be bent relative to the first haptic portion.